Add CLI Auto Best and target-size parity

[SLP-DEV1]

Summary

Bring the local CLI much closer to the GUI for the two highest-value compression workflows.

Auto Best

• add --auto-best
• mirror the GUI candidate strategy: WebP + JPEG for non-alpha images, WebP + PNG for alpha images
• include an explicit --format as an additional candidate when it is not already part of the set
• choose the smallest local candidate
• expose candidate size/format/quality/dimensions in JSON output

Target size

• add --target-size-kb <KB> plus --target-size <KB> alias
• mirror the GUI's up-to-seven-step quality search from quality 1 through the preferred quality
• return the highest JPG/WebP quality that reaches the requested target when possible
• report targetBytes and targetReached in CLI output/JSON
• allow Auto Best + target-size to be combined

Validation

CI now:

• syntax-checks the CLI
• performs the existing real WebP smoke test
• creates a noisy JPEG fixture and verifies target-size output is <= 20 KB with targetReached: true
• runs Auto Best and verifies multiple candidates plus an Auto Best selection are returned
• runs strict TypeScript and the production build

Docs

README examples/options/roadmap now reflect the new CLI capabilities and keep reSmush.it/Auto Compare clearly GUI-only.